\usemodule[zhfonts]
\startMPpage
input snail.mp;
Node foo.tex, snail.mp, luatex, mplib, foo.pdf;
foo.tex := io("foo.tex");
snail.mp := io("snail.mp");
luatex := proc("\LUATEX");
mplib := proc("MPLIB");
foo.pdf := io("foo.pdf");

as_star(foo.tex, luatex, "left");
as_planet(mplib, luatex, "top");
as_planet(snail.mp, mplib, "left");
as_star(foo.pdf, luatex, "right");

draw_each foo.tex, snail.mp, luatex, mplib, foo.pdf;
flow_each foo.tex => luatex, snail.mp => mplib, luatex => foo.pdf;
flow_each (luatex => mplib) shifted (-0.25 * (_bw_ luatex), 0);
flow_each (mplib => luatex) shifted (0.25 * (_bw_ luatex), 0);
\stopMPpage
